"There is no rule for it."
"Darn the rules!" I exclaim. "Ain't I here?"
"The thing is self-evident," I continue. "184 degrees west
longitude means a lapping over in east longitude of four degrees.
Besides I have been in east longitude all the time. I sailed from
Fiji, and Fiji is in east longitude. Now I shall chart my position
and prove it by dead reckoning."
But other troubles and doubts awaited me. Here is a sample of one.
In south latitude, when the sun is in northern declination,
chronometer sights may be taken early in the morning. I took mine
at eight o'clock. Now, one of the necessary elements in working up
such a sight is latitude. But one gets latitude at twelve o'clock,
noon, by a meridian observation. It is clear that in order to work
up my eight o'clock chronometer sight I must have my eight o'clock
latitude. Of course, if the Snark were sailing due west at six
knots per hour, for the intervening four hours her latitude would
not change. But if she were sailing due south, her latitude would
change to the tune of twenty-four miles. In which case a simple
addition or subtraction would convert the twelve o'clock latitude
into eight o'clock latitude. But suppose the Snark were sailing
southwest. Then the traverse tables must be consulted.
This is the illustration. At eight A.M. I took my chronometer
sight. At the same moment the distance recorded on the log was
noted. At twelve M., when the sight for latitude was taken. I
again noted the log, which showed me that since eight o'clock the
Snark had run 24 miles. Her true course had been west 0.75 south.
I entered Table I, in the distance column, on the page for 0.75
point courses, and stopped at 24, the number of miles run.
Opposite, in the next two columns, I found that the Snark had made
3.5 miles of southing or latitude, and that she had made 23.7 miles
of westing. To find my eight o'clock' latitude was easy. I had but
to subtract 3.5 miles from my noon latitude. All the elements being
present, I worked up my longitude.
But this was my eight o'clock longitude. Since then, and up till
noon, I had made 23.7 miles of westing. What was my noon longitude?
I followed the rule, turning to Traverse Table No. II. Entering the
table, according to rule, and going through every detail, according
to rule, I found the difference of longitude for the four hours to
be 25 miles. I was aghast. I entered the table again, according to
rule; I entered the table half a dozen times, according to rule, and
every time found that my difference of longitude was 25 miles. I
leave it to you, gentle reader. Suppose you had sailed 24 miles and
that you had covered 3.5 miles of latitude, then how could you have
covered 25 miles of longitude? Even if you had sailed due west 24
miles, and not changed your latitude, how could you have changed
your longitude 25 miles? In the name of human reason, how could you
cover one mile more of longitude than the total number of miles you
had sailed?
It was a reputable traverse table, being none other than Bowditch's.
The rule was simple (as navigators' rules go); I had made no error.
I spent an hour over it, and at the end still faced the glaring
impossibility of having sailed 24 miles, in the course of which I
changed my latitude 3.5 miles and my longitude 25 miles. The worst
of it was that there was nobody to help me out. Neither Charmian
nor Martin knew as much as I knew about navigation. And all the
time the Snark was rushing madly along toward Tanna, in the New
Hebrides. Something had to be done.
How it came to me I know not - call it an inspiration if you will;
but the thought arose in me: if southing is latitude, why isn't
westing longitude? Why should I have to change westing into
longitude? And then the whole beautiful situation dawned upon me.
The meridians of longitude are 60 miles (nautical) apart at the
equator. At the poles they run together. Thus, if I should travel
up the 180 degrees meridian of longitude until I reached the North
Pole, and if the astronomer at Greenwich travelled up the 0 meridian
of longitude to the North Pole, then, at the North Pole, we could
shake hands with each other, though before we started for the North
Pole we had been some thousands of miles apart. Again: if a degree
of longitude was 60 miles wide at the equator, and if the same
degree, at the point of the Pole, had no width, then somewhere
between the Pole and the equator that degree would be half a mile
wide, and at other places a mile wide, two miles wide, ten miles
wide, thirty miles wide, ay, and sixty miles wide.
All was plain again. The Snark was in 19 degrees south latitude.
The world wasn't as big around there as at the equator. Therefore,
every mile of westing at 19 degrees south was more than a minute of
longitude; for sixty miles were sixty miles, but sixty minutes are
sixty miles only at the equator. George Francis Train broke Jules
Verne's record of around the world. But any man that wants can
break George Francis Train's record. Such a man would need only to
go, in a fast steamer, to the latitude of Cape Horn, and sail due
east all the way around. The world is very small in that latitude,
and there is no land in the way to turn him out of his course.
